Trapping efficiency for foxes ( Vulpes vulpes ) in central New SouthWales: age and sex biases and the effects of reduced fox abundance

A total of 276 red foxes ( Vulpes vulpes ) was captured over 40 597 trap-nights during 1994–96 at three separate sites in central New South Wales, resulting in an overall trapping efficiency of one fox per 147 trap-nights. Trapping using multiple trap sets placed at carcases was 3.2 times more efficient than trapping using single trap sets. During 1994–95, when two of the sites suffered a severe drought, fox abundance declined to less than 0.2 foxes km–1 of spotlight transect; trapping efficiency at those sites also declined, to an average of one fox per 315 trap-nights. Mean trapping efficiency for non-drought periods was one fox per 135 trap-nights, 2.3 times more efficient than during the drought period. In 1995 and 1996, 353 foxes were shot in areas adjacent to each site. This gave the opportunity to compare sex and age biases between the trapped and shot samples: the ratio of males to females was significantly higher in the trapped sample than in the shot sample, and there was also a significantly higher ratio of adults to juveniles in the trapped sample than in the shot sample.